The present invention relates to the suppression of hydrogen sulfide from hydrocarbons or water. In particular, the invention relates to such suppression by chemical means.
Hydrogen sulfide (H.sub.2 S) is a highly flammable and toxic gas (toxic Threshold Limit Value --Time Weighted Value =10 ppm; Short Term Exposure Limit =15 ppm). Hydrogen sulfide is encountered in many oil and gas formations and is a significant health hazard to oilfield and refinery workers. Accordingly, suppression of H.sub.2 S in hydrocarbons, e.g., natural gas, crude oil, refined oil products, and associated water (including brine) is an important concern. Further, because of the large quantities of material to be treated, it is important to have a means of suppression that is economically efficient. Complicating the problem somewhat is the fact that some treatments will have excellent performance in one situation but poor performance in another. For instance, many treatments have undesirable side effects. Some treatments will alter the specifications of the material; e.g., viscosity, pour point, water emulsifying tendency, and some will contaminate the material with another hazardous substance; e.g., formaldehyde. Still further, the solubility of the treatment additive is sometimes a factor. All of these items often severely limit the chemistry available to scavenge hydrogen sulfide from a particular source.
One class of substances which is of particular importance with regard to hydrogen sulfide evolution is "heavy hydrocarbons" which, as used herein, means a crude oil or a refinery fractions in which at least 50 weight percent of the fraction has a boiling point of at least 240.degree. C. (at atmospheric pressure). Such materials include petroleum residua, grease, lube oil, gas oil, diesel fuel, and coker unit distillates. Because of conventional refining practices, H.sub.2 S suppression is not currently a significant issue for grease, lube oil, or gas oil, but could be in the future if refinery operations are altered.
The use of various aldehydes which react with hydrogen sulfide has been known in the prior art for sometime. For example, U.S. Pat. No. 2,426,318 discloses a method of inhibiting the corrosive action of natural gas and oil containing soluble sulfides on metals by utilizing certain aldehydes, preferably formaldehyde.
U.S. Pat. No. 4,680,127 suggests using glyoxal to reduce the amount of hydrogen sulfide in hydrogen sulfide-containing dry gaseous and wet gaseous media.
U.S. Pat. No. 4,515,759 discloses a process for removal of hydrogen sulfide from gas mixtures, particularly gas mixtures containing hydrocarbons, wherein the gas mixture is treated with a buffered aqueous solution of a water soluble nitrite, such as sodium nitrite.
Co-pending U.S. patent application Serial No. 07/388,210 now abandoned describes the suppression of hydrogen sulfide with the reaction product of an alkylenepolyamine and formaldehyde.
Co-pending U.S. patent application Serial No. 07/374,427 now abandoned, and a related case of which has issued as U.S. Pat. No. 5,169,411 describes the suppression of H.sub.2 S with a reaction product of an amine or polyamine with an aldehyde or ketone. This broad disclosure does mention cyclic aldehydes, but it does not contain any disclosure of heterocyclic aldehydes.
Bottino, et al, Can. J. Chem., Vol. 59 (1981) p. 1205-1207 discloses the reaction product of furfural (2-furancarboxaldehyde) and 2-pyrrolecarboxaldehyde with butyl amine, but does not suggest the use of these materials as H.sub.2 S scavengers. The article is merely a report of the type of structure formed by the reaction of these aldehydes and simple primary amines
Robertson, J. Org. Chem., Vol. 25 (1960), p. 47-49, shows the reaction sequence used by Bottino, supra.
Hoyer, Z. Anorg. Allgem. Chem., 336(3-4), 192-6 (1965), [C. Abs. 63-9434d]; Hoyer, Z. Anorg. Allgem. Chem., 5(6), 231-2 (1965), [C. Abs. 63-16150e]; and Gallagher, J. Inorg. Nucl. Chem., (1969), 31(5), 1449-58, C. Abs. 70-120672n]discloses the reaction product of furfural, 2-pyridinecarboxaldehyde or 2-thiophenecarboxaldehyde with ethylene diamine (1,2diaminoethane) but do not mention the suppression of H.sub.2 S. These articles report the preparation of metal complexes (Zn, Co, Cu, and Ni) and the hydrolysis of such complexes.